The objective of the Genetically Engineered Mouse (GEM) Resource is to aid Cancer Center investigators with the design and execution of experiments to utilize animal models for the investigation of the progression of cancer and for the preclinical evaluation of therapies for the treatment of cancer. Although the use of animal models provides an invaluable source of reagents for preclinical testing and the investigation of regulatory mechanisms in vivo in a physiologically regulated system, the use of animals is costly with respect to equipment, animal resources, and technical expertise. The GEM Core will serve as a resource for carrying out and training in the use of all animal manipulations needed in the Cancer Center. The GEM Core will minimize the cost of utilizing animal models in the Cancer Center by consolidating the equipment, expertise, and animal resources. This will ensure an efficient use of animal research at minimal cost. The GEM Core will serve Cancer Center investigators by aiding in the following tasks. 1. The GEM Core will generate transgenic mice by the micro injection of DMA into one-celled mouse embryos. 2. The GEM Core will generate mutant mice by the manipulation of mouse Embryonic Stem Cells. 3. The Core will preserve lines of mice by cryopreservation. 4 The Core will aid investigators with the importation and exporting of lines of mice. The accomplishments of these tasks will allow the GEM Core to serve as a repository for all genetically engineered mouse models and techniques for Cancer Center investigators and will ensure efficient use of animal resources by Cancer Center investigators. The Shared Resource Leader is Dr. Francesco DeMayo, who has an extensive track record in these areas